In the drive-trains of motor vehicles, particularly in the case of off-road vehicles, differential locks are often provided in transverse and/or longitudinal differentials in order to enable propulsion of the motor vehicle, particularly when the ground conditions are difficult and individual wheels or even entire axles slip. For this, in most cases a differential lock is made in the form of a frictional or interlocking clutch, which when actuated prevents a compensation movement of the differential concerned. At least in the case of an interlocking differential lock, it is first necessary to reduce any rotational speed difference at the differential lock before the differential lock can be engaged. Whereas classically this has to be carried out by the vehicle driver at the time, in that he reduces the drive torque in a controlled manner and thereby brings about a synchronization, systems are also known in which the synchronization required for the engagement of the differential lock is produced automatically.
Thus, DE 42 92 208 T1 describes a method for actuating a differential lock of a differential in a motor vehicle drive-train, such that when a driver of the vehicle issues a locking command the differential lock is engaged as soon as there is essentially no rotational speed difference at the differential lock. Specifically, this is brought about in that when the driver issues the locking command, a rotational speed of a drive machine of the motor vehicle is reduced in a controlled manner and thereby a reduction of a drive torque is produced, which results in a corresponding reduction of any rotational speed difference there might be at the differential lock. In this case the rotational speed of the drive machine is reduced for a certain time interval within which a reduction of the rotational speed difference sufficient for the engagement of the differential lock is to be expected. Directly after that, the differential lock is engaged in order to lock the differential concerned. These steps take place automatically following the issuing by the vehicle's driver of the locking command, i.e. the vehicle's driver does not actively have to reduce the rotational speed of the drive machine in order to reduce the slip in the area of the differential concerned.